   //生成随机数
    function randomNum(min,max){
      return Math.floor(Math.random()*(max-min)+min);
  }
  //生成随机颜色RGB分量
  function randomColor(min,max){
      var _r = randomNum(min,max);
      var _g = randomNum(min,max);
      var _b = randomNum(min,max);
      return "rgb("+_r+","+_g+","+_b+")";
  }
  //先阻止画布默认点击发生的行为再执行drawPic()方法
  document.getElementById("canvas").onclick = function(e){
      e.preventDefault();
      drawPic();
  };
  function drawPic(){
      //获取到元素canvas
      var $canvas = document.getElementById("canvas");
      var _str = new Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
          'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
          'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z');
      //循环组成验证码的字符串//设置随机数库
      var _picTxt = "";//随机数
      var _num = 4;//4个随机数字
      var _width = $canvas.width;
      var _height = $canvas.height;
      var ctx = $canvas.getContext("2d");//获取 context 对象
      ctx.textBaseline = "bottom";//文字上下对齐方式--底部对齐
      ctx.fillStyle = randomColor(180,240);//填充画布颜色
      ctx.fillRect(0,0,_width,_height);//填充矩形--画画
      for(var i=0; i<_num; i++){
          var x = (_width-10)/_num*i+10;
          var y = randomNum(_height/2,_height);
          var deg = randomNum(-45,45);
          var txt = _str[randomNum(0,_str.length)];
          _picTxt += txt;//获取一个随机数
          ctx.fillStyle = randomColor(10,100);//填充随机颜色
          ctx.font = randomNum(16,40)+"px SimHei";//设置随机数大小，字体为SimHei
          ctx.translate(x,y);//将当前xy坐标作为原始坐标
          ctx.rotate(deg*Math.PI/180);//旋转随机角度
          ctx.fillText(txt, 0,0);//绘制填色的文本
          ctx.rotate(-deg*Math.PI/180);
          ctx.translate(-x,-y);
      }
      for(var i=0; i<_num; i++){
          //定义笔触颜色
          ctx.strokeStyle = randomColor(90,180);
          ctx.beginPath();
          //随机划线--4条路径
          ctx.moveTo(randomNum(0,_width), randomNum(0,_height));
          ctx.lineTo(randomNum(0,_width), randomNum(0,_height));
          ctx.stroke();
      }
      for(var i=0; i<_num*10; i++){
          ctx.fillStyle = randomColor(0,255);
          ctx.beginPath();
          //随机画原，填充颜色
          ctx.arc(randomNum(0,_width),randomNum(0,_height), 1, 0, 2*Math.PI);
          ctx.fill();
      }
      cc= _picTxt;//返回随机数字符串
  }
  drawPic();

  function validateCode(){
      //获取显示区生成的验证码
      var tyzm =cc;
      //获取输入的验证码
      var inputCode = document.getElementById("inputCode").value;
      var aa = document.getElementById("num").value;
      var bb = document.getElementById("password").value;
      sessionStorage.setItem('username',aa);
      sessionStorage.setItem('userpwd',bb);
      //console.log(checkCode);
      //console.log(inputCode);
      if (inputCode.length <= 0){
          alert("请输入验证码！");
      }
      else if (inputCode.toUpperCase() != tyzm.toUpperCase()){
          alert("验证码输入有误！");

      }
      else{
          alert("注册成功！");
          zhuce.style.display = "none";
          login.style.display = "block";
      }
  }